SLVAFL5 September   2023 TPS61299

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction of Water Heater
  5. 2Low Voltage Start-up Boost Converter Introduction
    1. 2.1 General Introduction About TPS61299
    2. 2.2 Introduction about Traditional Start-up Process
    3. 2.3 Down Mode and Boost Mode Operation
  6. 3TPS61299 Ultra-low Voltage Start-up Design
    1. 3.1 Ultra Low Voltage Start-up Set up
    2. 3.2 The Way AVIN influence Start-up Process
    3. 3.3 The Way Vout Influence Start-up Process
    4. 3.4 The Way L Influence Start-up process
      1. 3.4.1 Why With the Larger Inductance, The Smaller PVIN Start-up Can Be Achieved?
      2. 3.4.2 Why Does The Inductance Continue to Increase, The Minimum PVIN to Start Up Is Not Lower
      3. 3.4.3 Why 80 mV Can Start Normally While 70 mV Fail to?
  7. 4Ultra-low Voltage Start-up Design
    1. 4.1 Test Waveform
  8. 5Summary
  9. 6References

2.2 Introduction about Traditional Start-up Process

Figure 2-1shows the traditional start up solution when power input (PVIN) and analog input ( PVIN ) are connected . Figure 2-2shows the Ultra power vin start up solution where PVIN and AVIN are powered separately. The internal start up process of the boost converter are the same.

GUID-20230830-SS0I-JTRF-C986-7MWWN4LTKTVB-low.svg Figure 2-1 Typical Schematic of Traditional Start-up Design
GUID-20230830-SS0I-D80B-TJWN-HXX0GJZVDKWF-low.svg Figure 2-2 Typical Schematic With Ultra Low Input Voltage Start-up Design

After the EN pin is tied to high voltage, the TPS61299 begins to startup, the process can be divided into 5 stages, as is shown in Figure 2-3.

Stage 1: When output voltage is lower than 0.5 V, device behavior is the same as short protection, to limits the output power for the short protection.

Stage 2: As output voltage is higher than 0.5 V, the device operates at the boundary of Discontinuous Conduction Mode (DCM) and Continuous Conduction Mode (CCM), and the inductor peak current is limited to around 350 mA during this stage.

Stage 3: After the output voltage reaches 1.8 V, the TPS61299 starts to detect the output voltage configuration from VSEL pins, then latches the configuration. The version detection time depends on the resistance at VSEL pin, the higher resistance, the longer version detection time. For example, for 5 V normal version, the TPS61299 needs about 170 us for version detection. The TPS61299 checks the VSEL pin by reducing the resistor setting option to a higher setting option until the user finds the setting configuration with a 10-µs clock.

Stage 4: After detecting the configuration, the TPS61299 begin to latch the reference output voltage and the VOUT begins ramping to the target. The TPS61299 does not sense the VSEL pin during operation, so changing the resistor during operation will not change the VSEL setting. Toggling the EN pin during operation is one way to refresh it.

Stage 5: After version detection, TPS61299 continues switching and output ramps up further. For the high input current limit version devices, such as 250 mA, 500 mA, 1.2 A and 1.9 A version, TPS61299 reduces the inrush current during start-up by limiting the inductor average current lower than 500 mA (input current limit to 250 mA for 250 mA version), when output voltage is lower than 2.5 V. For When output voltage ramped over 2.5 V the aforementioned input current limit is released and set to version definition level.

GUID-20230920-SS0I-JRG6-LMVM-W5VLDSDFPZBF-low.svg Figure 2-3 Start-up Process of TPS61299